Photovoltaic (“PV”) modules are large-area optoelectronic devices that convert solar radiation directly into electrical energy. PV modules are made by interconnecting individually formed and separate solar cells, e.g., multi-crystalline or mono-crystalline silicon solar cells, and then mechanically supporting and protecting the solar cells against environmental degradation by integrating the cells into a laminated PV module. The laminated modules generally comprise a rigid and transparent protective front panel or sheet, and a rear panel or sheet which is typically called a back-sheet. Forming a sandwiched arrangement between the front panel and back-sheet are the interconnected solar cells and an encapsulant which is transparent to solar radiation. The front panel and back-sheet encapsulate the solar cell(s) and provide protection from environmental damage. The primary function of the back sheet is to provide the low water vapor transmission, UV and oxygen barrier properties and necessary to protect the silicon wafers (photocells) from degradation induced by reaction with water, oxygen or UV radiation. Because the silicon wafers are generally encapsulated in ethylene vinyl acetate (EVA) the back-sheet material should adhere well to EVA when the components are laminated together in a thermoforming process.
US2006/0166023 describes back-side protective sheets for PV battery module comprising a vapor-deposited film of an inorganic oxide in a vacuum chamber. EP1134073 describes a gas barrier film comprising a vapor deposited film prepared by vapor-deposition in a vacuum chamber.
Documents WO 2008/147 184 and EP 2 226 832 A, both from applicant, disclose an atmospheric pressure plasma treatment apparatus and method.
JP 2003-171 770 A discloses an apparatus for creating an anti-reflective layer on a substrate, the apparatus comprising a plurality of discharge sections. However, JP 2003-171 770 does not disclose the conditions for creating an improved barrier layer.
WO 2009/031886 A by applicant also discloses an apparatus for plasma treatment having multiple treatment spaces. Again, the conditions for creating an improved barrier layer are not disclosed.